Electrodeposition of nickel



United States Patent 3,002,903 ELECTRODEPOSITION 0F NICKEL DonaldGardner Foulke, Watchung, Otto Kardos, Red Bank, and Herman Koretzky,Bellcville, N.J., assignors to Hanson-Van Winkle-Munning Company, acorporation of New Jersey No Drawing; Filed Sept. 26, 1958, Ser. No.763,455

12 Claims. (Cl. 204-49) This invention relates to electroplating and,more particularly, to electrodepositing nickel from an aqueous acidicnickel plating bath. The invention is based on the discovery thatwater-soluble bisulfite addition products of acetylenic compounds, whenincorporated in a nickel electroplating bath, particularly inconjunction with various sulfo-oxygen compounds, are capable ofpromoting the formation of excellent bright and ductile electrodepositsof nickel over a wide current density range.

The electrodeposition of nickel from a plating bath containing asulfo-aoxygen carrier brightener additive generally produces asemi-bright deposit at the cathode, particularly at the lower currentdensities. Increasing the current density frequently increases theoverall brightness of the deposit, but often induces the formation ofcloudy or hazy areas, especially at the low and middle current densityranges. When, however, a small quantity of the bisulfite additionproduct of an acetylenic compound is incorporated in the plating bathtogether with a sulfo-oxygen compound, the brightness capacity of thebath is extended, and the electrodeposit is ductile and bright over avery wide current density range.

Theoretically, there are at least two possible bisulfite additionproducts which may be formed from a given acetylenic compound.Disregarding the numerous optical and geometrical enantiomorphs whichchemical theory predicts may be formed, the addition of a bisulfite toan acetylenic bond proceeds in two successive stages, the first of whichresults in the formation of an initial bisulfite addition product which,in turn, reacts in the second stage to produce a second bisulfiteadduct. The extent of the reaction is dependent upon and thereforecontrolled by the molar proportions of bisulfite present in the reactionmixture. Although the proof of structure of each of the two adducts isfar from conclusive, the initial bisulfite addition product of anacetylenic compound appears to be an a,B-unsaturated sulfonic acid (orsulfonate) which is capable of undergoing further addi tion, in thepresence of excess bisulfite, to form the second adduct. The apparentstructure of this second bisulfite addition product is that of asaturated disulfonic acid (or disulfonate), in which the sulfonic acid(or sulfonate) groups are vicinal.

Because almost any acetylenic compound can be made to undergo bisulfiteaddition, that is can be made to react with a compound capable offorming a chain-carrying sulfite radical to form one or more bisulfiteaddition products, no single common structural feature can be advancedto unequivocally characterize all of these adducts. Instead, the adductsmay conveniently be characterized by designating the proportionateamount of bisulfite (or.

of any compound capable of forming a chain-carrying sulfite radical)used in the reaction mixture.

Following an exhaustive investigation into the chemistry of bisulfiteaddition to acetylenic bonds, it has been found that the bisulfiteaddition products prepared by reacting a water-soluble acetyleniccompound together with N times an equivalent weight of a compoundcapable of forming a chain-carrying sulfite radical, where N is equal tothe number of acetylenic bonds per molecule of the acetylenic compound,are unusually effective for promoting the formation of bright and evenbrilliant electrodeposits of nickel over a very wide current density3,002,903 Patented Oct. 3, 1951 "ice range when the bisulfite adduct isincorporated in an aqueous acidic nickel plating bath which alsocontains one or more sulfo-oxygen carrier brightener compounds.Moreover, the combined use of the sulfo-oxygen compound and thebisulfite addition product has been found to exert a synergistic effecton the brightening capacity of the bath as compared with the use ofeither additive a one.

Only very small quantities of the bisulfite adducts are required in theplating bath and, generally, concentrations as low as 0.1 millimole perliter are effective. In many cases, however, at least 1 millimole perliter of the bisulfite adducts should be employed to secure the fullbenefit of their presence in the bath. There appears to be no sharplydelineated upper limit on the concentration of these, bisulfite additionproducts, but there is generally no advantage in employing more than 100millimoles per liter, and in most plating baths substantially fullbenefit of its presence is achieved with 20 millimoles per liter, oreven less.

Any bisulfite addition product prepared by reacting a Water-solubleacetylenic compound with N times an equivalent weight of a compoundcapable of forming a chaincarrying sulfite radical, where N is equal tothe number of acetylenic bonds per molecule of the acetylenic compound,and which is capable of being dissolved in acid and does not undergodecomposition upon protonation may be selected for inclusion in theplating solution. Particularly satisfactory results have been obtainedby using thebisulfite adducts prepared from a-substituted ora,a-disubstituted acetylenic compounds, both of Which contain afunctional group on a carbon atom vicinal to the acetylenic bond. It isof course necessary that the a.- substituted or a,a'-disubstitutedacetylenic compounds used to prepare the bisulfite adduct contains atleast one acetylenic bond which is neither sterically nor electronicallyhindered from reacting with a chain-carrying sulfite radical.

A preferred process according to this invention for producing brightnickel deposits comprises electrodepositing nickel from an aqueousacidic solution of at least one nickel salt in which there is dissolvedfrom M; to grams per liter of a sulfo-oxygen carrier brightener togetherwith from about 1 to about 25 millimoles per liter of the bisulfiteaddition product of an inc-substituted acetylenic compound and N timesan equivalent weight of a compound capable of forming a chain-carryingsulfite radical, N being equal to the number of acetylenic bonds permoleclue of the acetylenic compound. The u-substituted acetyleniccompounds used in preparing this bisulfite adduct all contain thestructural configuration GEC :3

Rn in which R, is a substituent of the group consisting of hydrogen,alkoxy, formoxy, alkanoxy, halogen, and polyoxy groups having thestructure 30 -O[OH )H0]nH in which R is a substituent of the groupconsisting of hydrogen, methyl, chloromethyl, hydroxymethyl, ethenyl,and glycidyl, and n is an integer from 1 to 20. In addition, R, may alsobe an amino group having the structure in which each of R and R" areeither hydrogen, alkyl, or hydroxyalkyl. The synergistic effect of thebisulfite addition products prepared by these acetylenic compounds onthe brightening capacity of various sulfo-oxygen compounds is especiallypronounced when the bisulfite adducts are used in the nickel platingsolution together with one or more of the water-soluble sulfo-oxygencompounds natively, the bisulfite addition product may be recovered fromthe reaction mixture (either by crystallization or prepicitation), andthen added to the plating bath, the same plating results being obtainedin either case Alselected from the group consisting of unsaturated ali-5 though the bisulfite addition products may be used in phatic sulfonicacids, mononuclear and binuclear aromatic nickel plating baths inconcentrations as high as 100 sulfonic acids, heterocyclic sulfonicacids, mononuclear millimoles per liter, or even more, there is noparticular aromatic sulfinic acids, the alkali metal, ammonium,magadvantage to be gained from the higher concentrations, nesium, andnickel salts of these acids, and mononuclear and the adducts arepreferably used in the range of conaromatic sulfonamides andsulfonimides. centrations from about 1 to about 25, or even in thePreparation of the bisulfite addition products is genrelatively narrowrange from 1 to 10 millimoles per liter. erally accomplished byrefluxing an aqueous solution The bisulfite addition products preparedfrom a-subcontaining both the acetylenic compound and an alkali stitutedacetylenic compounds have been found to be unmetal bisulfite (orsulfite) until most of the bisulfite (or usually effective brighteningagents, especially when used sulfite) ion has been consumed. The rate atwhich biin a plating bath in conjunction with various sulfo-oxysulfiteion is consumed in the reaction has been found gen compounds.Particularly satisfactory results have to be susceptible to catalysis bypassing gaseous oxygen been obtained from the bisulfite additionproducts prethrough the reaction mixture or by adding a trace amountpared from tat-substituted acetylenic compounds having a of a freeradical initiator (i.e., benzoyl peroxide) to the structure representedby the formula reactants; the rate is sharply diminished by adding traceamounts of free radical inhibitors, such as hydroquinone l and similarantioxidants, to the reaction mixture. From R C:G R1 these observations,it may be concluded that bisulfite ada fim to an q y f bond p f y by aradical in which each of R and R are substituents of the group chainprocess, 1n which the chain-carrying steps may be 5 consisting fhydrogen, k l lk 1k 1 and postulated as Proceedmg Vla the followmgreactlon droxy-substituted, alkoxy-substituted, and amino-substiquenceituted alkyl, alkenyl, and alkynyl groups, and R is a sube stituent ofthe group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl,hydroxy-substituted, alkoxy-substis0i- -lCEO- O=O tuted, andamino-substituted alkenyl and alkynyl groups. e e In addition, R mayalso be a substituted-alkyl group having the structural configuration-o=o-+Hs0a -o=o.u+sos- 2 The exact nature of the chain-carrying sulfiteradical is not actually known, since a similar chain involving HSO canbe written. Both species (80 -6 and HSO have been proposed for theautoxidation of bisulfite and sulin wllich each of 4 and 5 aresubstituents 0f the group fite ions by oxygen, and hence either mightplausibly conslsti'ng f hydrogen. y a y y yl. and y; function as thetransitory intermediate which adds to the droxy-substltuted,alkoxy-substliuted, and ammo-Subsuacetylenic bond. No matter what thetransitory interme- 40 fi y alkenyl, and y y p Each of a diate radical,however, any compound which is capable and h in above formulas aresubstituents 0f the group of forming a chain-carrying sulfite radicalmay be used consisting of Y Y; y, Y, alkafloxy, halo to form thebisulfite adduct. The term compound capagen and P Y Y groups having thestructure ble of forming a chain-carrying sulfite radical denotes R0 thealkali metal or metal bisulfites, sulfites, and metabisulfites, as wellas sulfurous acid or gaseous sulfur'dioxide. B n All of these compoundsreact with acetylenic compounds In Whlch R0 15 a substltuent of thegroup conslstmg of to form bisulfite adducts which, in turn, may be usedin hydrogelb methyl, h m hyl, hydroXymethyl, ethenyl, nickel platingbaths in accordance with this invention. and glycldyl and n 15 a mergerm 1 to 8 and Even though all of the available evidence indicates Rb mayalso be an ammo group havmg the structure that bisulfite addition toacetylenic compounds is radical i R in nature, and that consequently thepredominant prodnot formed is the corresponding conjugated sulfonic acid(or sulfonate), the possibility that bisulfite or sulfite ions formcharge-transfer complexes with acetylenic bonds, or in which each of Rand R"- are substituents of the group that bisulfite or sulfite ionsundegro simple ionic addition Consisting of hydrogen, y and y y y The toan acetylenic bond, cannot be completely dismissed. compounds listed inTable I are examples of various a-sub- After the bisulfite adduct hasbeen prepared, the reacstituted acetylenic compounds which may be usedto pretion mixture may be added directly (or decolorized and parebisulfite addition products which, in turn, may be then added directly)to the nickel plating bath or, alteremployed successfully in embodimentsof this invention.

TABLE I tat-Substituted acetylenic compounds Compound R1 R; Ra a3-butyne l,2-di0l I i HzOH 4-H H OH 3-methyl-1-butyu-3-ol --CH3 -on, H.-o11 3-methyl-1-pentyn-3-ol C,H5 OH; H -0H 2-propyn-1- -H V -H H ''-OH2,S-dimethyI-I-o ten B-yn-E-Ol -o u1 --oH,' pm 0H 1 The bisulfiteaddition products of each of the acetylenic compounds listed in Tables Iand H are prepared by refluxing an aqueous solution of the particularacetylenic compound with N times an equimolar proportion of a compoundcapable of forming a chain-carrying sulfite radical, preferably analkali metal bisulfite, N being equal to the number of acetylenic bondsper molecule of the acetylenic compound. These adducts readily dissolve,

without decomposition, in aqueous acidic plating baths,

and are unusually effective in such bathsboth in'promoting the formationof bright and ductile nickel electrodeposits over wide current densityranges and in extending the brightening range of sulfo-oxygen carrier"brightener additives.

The compounds listed in Table III are examples of sulfo-oxygen compoundswhich, when used in the plating bath in conjunction with the bisulfiteaddition product of an acetylenic compound, extend the current densityrange over which the formation of ductile and bright nickelelectrodeposits may be obtained. These sulfooxygen compounds may be usedover a very wide range of concentrations to 80 grams per liter), butpreferably are used in an amount in the range from about 1 to about 20grams per liter.

TABLE 111 Organic sulfa-oxygen compounds (1) Unsaturated aliphaticsulfonic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof:

Sodium vinyl sulfonate, H C=CHSO Na Sodium allyl sulfonate, H @CHCH SONa (2) Mononuclear aromatic sulfonic acids, and alkali metal, ammonium,magnesium, and nickel salts thereof:

Benzene monosulfonic acid, C H SO H Sodium benzene monosulfonate, C H SONa Nickel benzene monosulfonate, (C I-I SO Ni Sodium p-toluenemonosulfonate, CH C H SO Na p-Chlorobenzene sulfonic acid, ClC H SO HSodium p-chlorobenzene sulfonate, ClC H SO Na Sodium p-bromobenzenesulfonate, BrC H SO Na 1,2-dichlorobenzene sulfonic acid, Cl C H SO H1,2- or 2,5-dichlorobenzene sulfonate sodium salt,

Cl C H SO Na Sodium m-benzene disulfonate, C H (SO Na) m-Benzenedisulfonic acid, C H (SO H) Nickel m-benzene disulfonate, C H (SO Nio-Sulfobenzoic acid monoammonium salt,

HOOC-C H SO NH 1-Amino-2,5-benzene disulfonic acid,

o-Aminobenzene sulfonic acid, H NC H SO H (3) Mononuclear aromaticsulfinic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof:

Sodium benzene sulfinate, C H SO Na Sodium p-toluene sulfinate, CH C HSO Na (4) Mononuclear aromatic sulfonamides and sulfonimides:

Benzene sulfonamide, C H SO NH p-Toluene sulfonamide, CH C H SO NHo-Sulfobenzoic imide, C H CONHSO Benzyl sulfonamide, C H CH SO NHBenzene sulfhydroxamic acid, C H SO NHOH -N,N-dimethyl-p-toluenesulfonamide,

CH C H SO N(CH N,N-dicarboxyethyl benzene sulfonamide,

C H SO N(C H COOH) (5) Binuclear aromatic sulfonic acids, and alkalimetal,

ammonium, magnesium, and nickel salts thereof: 2-naphthalenemonosulfonic acid, C H- SO H 1,5- or 2,7-naphthalene,disu1fonic acid,

8 Nickel 1,5- or 2,7-naphthalene disulfonate,

Sodium naphthalene trisulfonate, C I-I (SO Na) Naphthalene trisulfonicacid, C H (SO H) Diphenyl p,p-disulfonic acid,

2-naphthol-3,6-disulfonic acid, HOC H (SO H) Sodium2-naphthol-3,6-disulfonate,

1-naphthylamine-3,6,8-trisulfonic acid, 2 1o 4( 3 )s (6) Heterocyclicsulfonic acids, and alkali metal, am-

monium, magnesium, and nickel salts thereof:

Thiophene sulfonic acid, C H S-SO H Sodium thiophene sulfonate, C HS-SOgNa 2-(4-pyridyl)ethyl sulfonic acid, C H N-C H SO H For the mostpart, only the free sulfonic acids are listed in Table III. However, thealkali metal, ammonium, magnesium, and nickel salts of these acids arein all cases the full equivalent of the corresponding sulfonic acid, andmay be used in its place in carrying out the process of the invention.

The following examples are illustrative of the effectiveness with whichthe bisulfite addition product of acetyleniccompounds may be used inconjunction with various sulfooxygen compounds in accordance with thisinvention. In each example, Watts nickel plating bath having thefollowing basic composition was used:

Grams per liter Nickel sulfate, NiSO -7H O 300 Nickel chloride, NiCl -6HO 45 Boric acid, H 30 41.25

.Unless otherwise indicated, plating operations in each example werecarried out in a Hull test cell on brass .cathodes so that the effect ofa wide range of current densities could be observed. The pH of the bathwas adjusted to 3.2 with sulfuric acid, and the electrodeposits Wereformed at a temperature of 60 C. using a total current of 2 amperes anda plating time of about 10 minutes. The average thickness of eachelectrodeposit was 0.025 mm. (0.001 inch). No agitation was provided.

, In several of the examples, the electrodeposits were formed in an openvessel on polished steel cathodes, using vigorous air agitation and anaverage current density of 60 amperes per square foot and the same bathtemperature and pH as previously indicated. The leveling effect exertedby the bath, which is a measure of the decrease in roughness 'of thenickel electrodeposit compared to that of the underlying metal surface,was calculated in each of these examples. To determine the levelingeffect exerted by the bath the roughness value (root mean square valuein microinches) of the steel panel was measured with a Brush SurfaceAnalyzer prior to the plating operation. The roughness value of theplated panel was similarly measured immediately following the platingoperation, and the leveling effect then calculated according to thefollowing equation:

where L=leveling effect (percent); R =initial roughness value (R.M.S.value in microinches) of the steel panel; and R =final roughness value(R.M.S. value in microinches) of the nickel electrodeposit on the panel.

EXAMPLE I The bisulfite addition product of Z-butyne-lA-diolwa preparedby refluxing equimolar proportions of Z-butyne- 1,4-diol (in the form ofa 36 percent aqueous solution) and sodium bisulfite. After refluxing thereaction mixture for about 7 /2 hours, it was diluted with water,treated with activated carbon and filtered, yielding a very light yellowsolution. Titration of an aliquot of the filtrate with standardiodine-potassium iodide reagent, using starch as an indicator, showedthat only 2.6 mole percent of the original sodium bisulfite had remainedunreacted. From both the infrared spectrum and the chemical propertiesof the bisulfite addition product, it may be adduced that thepredominant product formed during the reaction was sodiuml,4-dihydroxy-Z-buteneZ-sulfonate. The bisulfite addition product couldbe used in nickel plating baths without further purification, or itcould be precipitated or crystallized from solution and then redissolvedin the plating bath, the plating results being the same in either case.

Table IV summarizes the results of a series of tests which demonstratethe brightening effect on the basic Watts plating bath of variousconcentrations of representative sulfo-oxygen compounds, alone and incombination with the bisulfite addition product of equimolar quantifiesof 2-butyne-l,4-diol and sodium bis'ulfite described immediately above.The plating operations were carried out both in a Hull test cell onbrass cathodes and in an open vessel on a steel panel which had beenpolished to give an initial surface roughness value of aboutmicroinches.

TABLE IV sulfite addition product exerted a pronounced leveling effecton the bath during the plating operation.

EXAMPLE III Equimolar proportions of 1,4-diacetoxy-2butyne and sodiumbisulfite were dissolved in water and the solution refluxed for about 5hours. The reaction mixture was diluted with water, decolorized withactivated carbon, filtered under suction, and the filtrate used in theplating bath without turther purification.

When 4.4 millimoles per liter of bisulfite addition product were addedto a Watts plating bath which had substantially the same composition (innickel sulfate, nickel chloride, and boric acid) of Example I and whichcontained 3 grams per liter of sodium naphthalene-1,3,6- trisulfonate,the nickel deposit formed on the test panel of a Hull cell was verybright and ductile over the current density range of from 10 to 60amperes per square foot. Increasing the concentration of the bisulfiteadduct to 8.8 millimoles per liter did not substantially increase thebrightness.

EXAMPLE IV To a dilute aqueous solution of l,4-di(;3-hydroxyethoxy)-2-butyne was added an equimolar quantity of sodium bisulfite and thereaction mixture refluxed for about 7 hours. After cooling, the solutionwas further diluted with water, treated with activated carbon, andfiltered under suction, yielding an almost colorless filtrate. The

Cumulative efiect of the bisulfite addition product of 2-butyne-1,4-di0l on bright nickel plating Character of eleetrodepositElectrolytic cell Open vessel Bisulfite Sulfa-oxygen compound Cone.Adduct (gm./1.) (mmoles/l Current density Appearance range of AppearanceLeveling maximum (percent) brightness (a.s.f.)

Sodium napthalene-l,3,6-trisulfonate. 8. 0 0.0 Semi-bright, hazy 22. 54. 4 Bright 1. 5 4. 4 Sodium benzenesulfonate 16.0 0.0 Semi-bright,slight haze... 1. 5 4. 4 Bright 22. 5 4. 4 Brilliant. 54

EXAMPLE II An aqueous solution containing equivalent quantities of4-methoxy-2-butyn-1-ol and potassium bisulfite was heated to reflux forseveral hours. After cooling, the solution was decolorized withactivated carbon, filtered under suction, and methanol slowly added tothe filtrate until no further precipitation occurred. The precipitatewas filtered, dried in vacuo, and used in the plating bath withoutfurther purification.

A Watts nickel plating bath was prepared containing 300 grams per literof nickel sulfate, grams per liter of nickel chloride, 41.25 grams perliter of boric acid, and 1.5 grams per liter of sodiumnaphthalene-1,3,6-trisulfonate. After adjusting the pH of the bath to3.2 with sulfuric acid, an electrodeposit of nickel was formed on asteel panel in an open vessel, using a bath temperature of 60 (3., mildair agitation, and an average current density of 60 amperes per squarefoot. The electro deposit was only semi-bright and marred by hazy areasat the edges. Upon adding 8.8 millimoles per liter of the bisulfiteaddition product of equimolar quantities of 4- methoxy-Z-butyn-l-ol andpotassium bisulfite (the preparation of which is described above) tothis bath, a fully brilliant nickel electroplate free from clouds wasformed over the entire surface of the panel. The difierence in roughnessvalues ofthis electroplate and the unplated polished steel panel was 52percent, indicating that the bipredominant product formed during thereaction was sodium 1,4-di-(B-hydroxyethoxy)-2-butene-2-sulfonate.

An electrodeposit of nickel was formed on a panel of polished steel inan open vessel, using a basic Watts bath having substantially the samecomposition (in nickel sulfate, nickel chloride, and boric acid)described previously. The deposite formed at a bath temperature of 60 C.and at a pH of 3.1 to 3.5 was matte. Upon adding 1.5 grams per liter ofsodium naphthalene-1,3,6-trisulfonate and 4.4 millimoles per liter ofthe bisulfite adduct of l,4-di-(,B-hydroxyethoxy)-2-butyne to this bath,a bright to brilliant nickel electrodeposit was formed under the sameplating conditions. Measurement of the roughness values (root meansquare value in microinches) of both the unplated and brilliantly platedpanel, using a Brush Surface Analyzer, showed that the roughness of theplated panel had decreased by over 70 percent from that of the unplatedpanel, indicating that the use of the bisulfite addition product in thebath is accompanied by leveling during the plating operation.

EXAMPLE V The bisulfite addition product of 1,4-di-(B-hydroxy-'y-chloropropoxy)-2-butyne, which is the reaction product of2-butyne-1,4-d'iol and epichlorohydrin, was prepared by adding anequimolar proportion of 1,4-di-(B-hydroxy- 7-ch1oropropoxy)-2-butyne toan aqueous solution of sodium bisulfite and refluxing the mixture forseveral hours. After cooling, the solution was diluted, decolorized withactivated carbon, and filtered. Methanol was added to the filtrate, withvigorous stirring, to precipitate the bisulfite addition product. Afterfiltration, the precipitate was dried in vacuo and used without furtherpurification.

A very bright and ductile electrodeposit of nickel was formed on apolished steel panel in an open vessel using a plating bath and platingconditions similar to those described in Example IV with the soleexception that 2.2 millimoles per liter of the bisulfite additionproduct of 1,4-di-(fl-hydroxy-y-chloropropoxy)-2-butyne (the preparation of which is described immediately above) was used in the bath inplace of the bisulfite adduct of 1,4-di-(fihydroxyethoxy) -2-butyne. Theleveling etfect was 56 percent, indicating that the use of the bisulfiteaddition product in the bath is accompanied by leveling.

EXAMPLE VI Equimolar proportions of sodium bisulfite and 4-N,N-diethylamino-Z-but-yn-l-ol were dissolved in water and the mixtureheated to reflux for about 4 hours. The mixture was diluted toapproximately twice its volume with water, decolorized with activatedcarbon, filtered under suction, and the filtrate evaporated undervacuum, yielding a yellow powder which decolorizes on standing in air.The bisulfite adduct was recrystallized from water prior to use in aplating bath.

When nickel was electrodeposited in at Hull test cell at 50 C. to 60 C.from a high chloride nickel plating bath (pH=3.2 to 3.5) containing 150grams per liter of" nickel sulfate, 248 grams per liter of nickelchloride, f

41.2 grams per liter of boric acid, and 7.5 grams per liter of sodiumnaphthalene-1,3,6-trisulfonate, the resultant electroplate was onlysemi-bright in the medium current density range of the test panel. Uponthe addition of 4.4 millimoles per liter of the recrystallized bisulfiteaddition product described above to this bath, a very bright nickeldeposit was formed over the current density range of from 1 to 80amperes per square foot.

Using the same bath and identical plating conditions in an open vessel,except that 1 gram per liter of sodium 7 benzene-1,5-disulfonate wasused in place of the sodium naphthalenea'l,3,6-trisulfonate and mild airagitation was provided, a nickel electrodeposit of 0.001 inch was formedon a roughened steel panel. ing operation, the surface roughness of thepanel has been reduced by over 40 percent, demonstrating the levelingefiect exerted by the bisulfite adduct.

EXAMPLE VII Excellent results are also obtained when the. electroplateis formed from a plating bath containing the bisulfite addition productof an acetylenic compound containing one or more primary amino groups.To illustrate this principle, the bisulfite addition product of 1,4-diamino-Z-butyne was prepared in the standard manner by refluxingequivalent weights of 1,4-diamino-2-butyne and sodium bisulfite in anaqueous medium. The bisul: fite adduct was precipitated from the aqueoussolution and dried in vacuo prior to use.

A semi-bright nickel deposit, marred by haziness, was formed on apolished brass panel in a Hull cell from a standard Wattssulfate-chloride-boric acid bath containing 3 grams per liter of sodiumnaphthalene-1,3,6-trisulfonate. The plating operation was conducted by atemperature of 50 C. and at a total current of two amperes. No agitationwas provided. By adding only 4.4 millimoles per liter of the bisulfiteaddition product of equimolar quantities of 1,4-diamino-2-butyne and abisulfite (as described above) to this bath, a very bright deposite freefrom haze was formed over the current density range of from 1 to 50amperes per square foot. Increasing the concentration of the bisulfiteadduct further increased the brightness of the electrodeposit.

Following the plat: H

EXAMPLE VIII Halogen-substituted acetylenic compounds also formbisulfite addition products which are exceptionally effective synergistswhen used in conjunction with a sulfooxygen brightening agent in nickelplating baths. In a Watts plating bath of the basic inorganic saltcomposition of Example II, containing 1.5 grams per liter of sodiumnaphthalene-l,3,6-trisulfonate, semi-bright deposits were obtained atcurrent densities of from 20 to 40 amperes per square foot at a pH of3.2 and a bath temperature of 55 to 60 C., with no agitation. However,when 4.4 millimoles per liter of the bisulfite addition product ofequivalent weights of 1,4-dichloro-2-butyne and sodium bisulfite wasadded to this bath, the nickel deposit formed under these sameconditions was exceptionally bright over the current density range from10 to amperes per square foot.

EXAMPLE IX In each of the previous examples, the bisulfite additionproduct was prepared from an oz,ot'-dlSl.lbStltUtd acetylenic compoundin which the same or different functional groups were present on carbonatoms adjacent to the acetylenic bond. The bisulfite addition productsof tat-substituted acetylenic compounds, containing a single functionalgroup on a carbon vicinal to the acetlyenic bond, have also provedexceptionally effective in nickel plating baths containing asulfo-oxygen brightening agent.

7 Table V sets forth in detail the concentrations of the bisulfiteaddition product of a number of a-substituted acetylenic compounds(containing a single functional group) added to a standard Watts bathwhich also contained 4 grams per liter of sodium naphthalene-1,3,6-trisulfonate, and the character of the deposits produced from the bath.Each of the bisulfite adducts was prepared by refluxing equimolarquantities of the acetylenic compound and sodium bisulfite in aqueousmedium for several hours, diluting the reaction mixture with water,decolorizing the mixture with activated carbon, filtering it undersuction, and precipitating the bisulfite addition product from thefiltrate by the addition of methanol. Plating operations were carriedout in -a Hull test cell on polished brass cathodes for a period of 10minutes using a bath temperature of '55" C., a pH of 3.2, and a totalcurrent of two amperes. No agitation was provided.

EXAMPLE X a,fl-Disubstituted acetylenic compounds containing the same ordifferent functional groups on carbon atoms alpha and beta to theacetylenic bond, may also be used to prepare a bisulfite additionproduct for use in nickel plating baths in accordance with theinvention. For example, the bisulfite addition product of 3-butyne-1,2-diol was prepared by refluxing the alkyndiol with an equimolar quantityof sodium bisulfite in an aqueous medium for 7 to 8 hours. Afterdecolorizing the reaction mixture with activated carbon, it was filteredand the filtrate concentrated under vacuum until the bisulfite additionproduct began to crystallize. The concentrated filtrate was cooled in anice chest, yielding a aooaoos powdery bisulfite addition product whichcould be used without further purification.

To a standard Watts sulfate-chloride-boric acid plating bath was added 4grams per liter of sodium naphthalene 1,3,6-trisulfonate. A test panelwhich received a nickel electroplate firom this bath was semi-brightover a wide current density range, but exhibited slight haziness in thelow and middle current density range. By adding 4.4 millimoles per literof the bisulfite addition product of 3-butyne-l,2-diol to theelectroplating solution, the

. nickel deposit became brilliant over the entire current density rangeof the panel. Increasing the concentration of the bisulfite additionproduct to 8 or 10 millimoles per liter did not increase the brightnessnor extend the range further.

EXAMPLE XI Bisulfite addition products prepared from polyacetyleniccompounds, in which the molecular structure contains two or moreacetylenic bonds, have also proved exceptionally effective in nickelplating baths containing sulfo-oxygen brightening additives. Inpreparingthese bisulfite addition products, the amount of bisulfite used may varyfrom an equimolar quantity (based on the molar proportion ofpolyacetylenic compound) to N times an equimolar quantity, where N isthe number of acetylenic bonds per molecule of the polyacetyleniccompound. Where only an equimolar quantity of bisulfite is reacted withthe polyacetylenic compound, then the amount of unsaturation in theresultant adduct will be greater than when a stoichiometric quantity (Ntimes an equimolar amount) of the bisulfite is employed. Both adductsmay be used in nickel plating baths with equal facility.

Two diiferent bisulfite addition products were prepared from2,4-hexadiyne-l,6-diol, using two equivalents of sodium bisulfite in thefirst case and an equimolar quantity in the second. The first bisulfiteaddition prodnot was prepared by dissolving in water one equivalent of2,4-hexadiyne-1,6-diol for each two equivalents of sodium bisulfite andrefluxing the mixture for about 6 hours. The solution was decolorizedwith activated carbon, filtered under suction, and the filtrateevaporated under vacuum, leaving the bisulfite addition product as alight tan powder. A similar procedure was used to prepare the secondbisulfite addition product except that equimolar proportions of sodiumbisulfite were employed in the reaction mixture. The work-up, however,was the same in both cases. To distinguish between the two adducts, theformer (first) bisulfite addition product was designated as the bimolaradduct while the latter (second) was termed the equimolar bisulfiteaddition product.

Table VI sets forth the results observed when nickel waselectrodeposited in a Hull cell on brass cathodes from a standard Wattsplating bath containing varying concentrations of a representativesulfo-oxygen compound (sodium naphthalene-1,3,6-trisulfonate) togetherwith one of the two bisulfite adducts.

In the foregoing examples of the invention, the bisulfite additionproducts of acetylenic compounds were used successfully in the standardWatts nickel electroplating bath, which is prepared by dissolving nickelsulfate, nickel chloride, and boric acid in water. Similar i iadvantages are also attained when the bisulfite addition product isdissolved in other types of aqueous acidic nickel electroplating baths.For example, the bisulfite adducts are beneficial when used in straightnickel sulfate baths, in straight nickel chloride baths, and in variousother nickel plating baths based on using nickel formate, nickelsulfamate, or nickel fluoborate as the nickel salt which is dissolved inthe aqueous acidic solvent, and consequently the invention is applicableto electrodeposit-ion from any aqueous acidic solution of one or morenickel salts.

We claim:

1. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution in which thereis dissolved from about A to about grams per liter of a water-solublesulfooxygen compound of the group consisting of unsaturated aliphaticsulfonic acids, mononuclear and binuclear aromatic sulfonic acids,heterocyclic sulfonic acids, mononuclear aromatic sulfinic acids, thealkali metal, ammonium, magnesium, and nickel salts of said acids, andmononuclear aromatic sulfonarnides and sulfonimides, and from about 1 toabout 25 millimoles per liter of a water-soluble bisulfite additionproduct of an oz-Substituted acetylenic compound and N times anequivalent weight of a compound capable of forming a chain-carryingsulfite radical, where N is equal to the number of acetylenic bonds permolecule of the acetylenic compound, said u-substituted acetyleniccompound containing the structural configuration CEC-( I]- B in which Ris a substituent of the group consisting of hydroxy, alkoxy, formoxy,alkanoxy, halogen, polyoxy groups having the structure R0 O[CH;,CIEHO]DHin which R is a substituent of the group consisting of hydrogen, methyl,chloromethyl, hydroxymethyl, ethenyl, and glycidyl, and n is an integerfrom 1 to 20, and amino groups having the structure in which each of Rand R" are substituents of the group consisting of hydrogen, alkyl, andhydroxyalkyl, said compound capable of forming a chain-carrying sulfiteradical being selected from the group consisting of sulfurous acid,sulfur dioxide, and the alkali metal and metal bisulfites, sulfites, andmetabisulfites, said bisulfite addition product containing thestructural configuration CH=C- SIOSM in which M is a cation substituentselected from the group consisting of hydrogen, alkali metals, ammonium,magnesium, and nickel, and the olefinic carbon atom to which the $0 Mradical is attached was originally one of the acetylenic carbon atoms.

2. The process for producing bright nickel deposits which compriseselectrodepositiing nickel from an aqueous acidic solution of at leastone nickel salt in which there is dissolved from about A to about 80grams per liter of a water-soluble sulfo-oxygen compound of the groupconsisting of unsaturated aliphatic sulfonic acids, mono-nuclear andbinuclear aromatic sulfonic acids, heterocyclic sulfonic acids,mononuclear aromatic sulfinic acids, the alkali metal, ammonium,magnesium, and nickel salts of said acids, and mononuclear aromaticsulfonamides and sulfonimides, and from about 1 to about 25 millimolesper liter of a water-soluble bisulfite addition product of anu,a'-disubstituted acetylenic compound and N times an equivalent weightof a compound capable of forming a chain-carrying sulfite radical, whereN is equal to the number of acetylenic bonds per mole cule of theacetylenic compound, said OL,Ot'-dlSllbStltlltd acetylenic compoundcontaining the structural configuration in which each of R and R aresubstituents of the group consisting of hydroxy, alkoxy, formoxy,alkanoxy, halogen, polyoxy groups having the structure 0[0H2( 3H-0]n ]1in which R is a substituent of the group consisting of hydrogen, methyl,chloromethyl, hydroxymethyl, ethenyl, and glycidyl, and n is an integerfroml to 20, and amino groups having the structure in which each of Rand R" are substituents of the group consisting of hydrogen, alkyl, andhydroxyalkyl, said compound capable of forming a chain-carrying sulfiteradical being selected from the group consisting of sulfurous acid,sulfur dioxide, and the alkali metal and metal bisulfites, sulfites, andmetabisulfites, said bisulfite addition product containing thestructural configuration in which M is a cation substituent selectedfrom the group consisting of hydrogen, alkali metals, ammonium,magnesium, and nickel, and the olefinic carbon atom to which the $0 Mradical is attached was originally one of the acetylenic carbon atoms.

3. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution in which thereis dissolved from about A to about 80 grams per liter of a water-solublesulfooxygen compound of the group consisting of unsaturated aliphaticsulfonic acids, mononuclear and binuclear aromatic sulfonic acids,heterocyclic sulfonic acids, mononuclear aromatic sulfinic acids, thealkali metal, ammonium, magnesium, and nickel salts of said acids, andmononuclear aromatic sulfonamides and sulfonimides, and from about 1 toabout 25 millimoles per liter of a water-soluble bisulfite additionproduct of an u-Sllbstituted acetylenic compound and N times anequivalent weight of a compound capable of forming a chain-carryingsulfite radical, where N is equal to the number of acetylenic bonds permolecule of the acetylenic compound, said u-substituted acetyleniccompound having a structure represented by the formula R2 RzCECC IR1 inwhich each of R and R are substituents of the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, andhydroxy-substituted,alkoxy-substituted, and amino-substituted alkyl, alkenyl, and alkenylgroups, R is a substituent of the group consisting of hydrogen, halogen,alkyl, alkenyl, alkynyl, hydroxy-substituted, alkoXysubstituted, andamino-substituted alkenyl and alkynyl groups, and isubstituted-alkylgroups having thetstructural configuration R4 Rain 16 in which each ofthe R and R are substituents of the group consisting of hydrogen, alkyl,alkenyl, alkynyl, and hydroxy-substitut'ed, alkoXy-substituted, andamino-substituted alkyl, alkenyl, and alkynyl groups, and each of R andR are substituents of the group consisting of hydroxy, alkoxy, formoxy,alkanoxy, halogen, polyoxy groups having the structure in which R is asubstituent of the group consisting of hydrogen, methyl, chloromethyl,hydroxymethyl, ethenyl, and glycidyl, and n is an integer from 1 to 20and amino groups having the structure in which each of R and R" aresubstituents of the group consisting of hydrogen, alkyl, andhydroxyalkyl, said compound capable of forming a chain-carrying sulfiteradical being selected from the group consisting of sulfurous acid,sulfur dioxide, and the alkali metal and metal bisulfites, sulfites, andmetabisulfites, said bisulfite addition product containing thestructural configuration EiO M in which M is a cation substituentselected from the group consisting of hydrogen, alkali metals, ammonium,magnesium, and nickel, and the olefinic carbon atom to which the $0 Mradical is attached was originally one of the acetylenic carbon atoms.

4. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution of at least onenickel salt in which there is dissolved from about A to about 80 gramsper liter of a water-soluble sulfo-oxygen compound of the groupconsisting of unsaturated aliphatic sulfonic acids, mononuclear andbinuclear aromatic sulfonic acids, heterocyclic s'ulfonic acids,mononuclear aromatic sulfonic acids, the alkali metals, ammonium,magnesium, and nickel salts of said acids, and mononuclear aromaticsulfonamides and sulfonimides, and from about 1 to about 25 millimolesper liter of a water-soluble bisulfite addition product of anoc,oc'-diSubStitl1ted acetylenic compound and N times an equivalentweight of a compound capable of forming a chain-carrying sulfiteradical, where N is equal to the number of acetylenic bonds per moleculeof the acetylenic compound, said a,a' -disubstituted acetylenic compoundhaving a structure represented by the formula in which each of R R R andR are substituents'of the group consisting of hydrogen, alkyl, alkenyl,alkynyl, and hydroxy-substituted, alkoxy-substituted, andaminosubstituted alkyl, alkenyl, and alkynyl groups, and each of R and Rare substituents of the group consisting of hydroxy, alkoxy, formoxy,alkanoxy, halogen, polyoxy groups having the structure. a

R0 -o-[cH2( H0],,H in which Ris a substituent of the group consisting ofhydrogen, methyl, chloromethyl, hydroxymethyl, ethenyl,

and glycidyl, and n is an integer from 1 to 20, and amino groups havingthe structure RI! 7 V p in which each of R and R" are substituents ofthe group 17 consisting of hydrogen, alkyl, and hydroxyalkyl, saidcompound capable of forming a chain-carrying sulfite radical beingselected from the group consisting of sulfurous acid, sulfur dioxide,and the alkali metal and metal bisulfites, sulfites, and metabisulfites,said bisulfite addition product containing the structural configurationin which M is a cation substituent selected from the group consisting ofhydrogen, alkali metals, ammonium, magnesium, and nickel, and theolefinic carbon atom to which the 80 M radical is attached wasoriginally one of the acetylenic carbon atoms.

5. The process for producing bright nickel deposits according to claim3, wherein the bisulfite addition prodnot is formed from an u-hydroxyacetylenic compound having a structure represented by the formula $2Ra-CEC-(E-Rr 6. The process for producing bright nickel depositsaccording to claim 3, wherein the bisulfite addition prodnet is formedfrom an a-haloacetylenic compound having a structure represented by theformula 7. The process for producing bright nickel deposits according toclaim 3, wherein the bisulfite addition product is formed from ana-polyoxy acetylenic compound having a structure represented by theformula 8. The process for producing bright nickel deposits according toclaim 3, wherein the bisulfite addition product is formed from anu-polyoxy acetylenic compound having a structure represented by theformula 18 9. The process for producing bright nickel deposits accordingto claim 4, wherein the bisulfite addition product is formed from ana,a-disubstituted acetylenic compound having a structure represented bythe formula 10. The process for producing bright nickel depositsaccording to claim 4, wherein the bisulfite addition product is formedfrom an a,a'-disubstituted acetylenic compound having a structurerepresented by the formula 11. The process for producing bright nickeldeposits according to claim 4, wherein the bisulfite addition product isformed from an u,oz'-diSLIbStitl1ted acetylenic compound having astructure represented by the formula 12. The process for producingbright nickel deposits according to claim 4, wherein the bisulfiateaddition 634,394 Great Britain Mar. 22, 1950

1. THE PROCESS FOR PRODUCING BRIGHT NICKEL DEPOSITS WHICH COMPRISESELECTRODEPOSITING NICKEL FROM AN AQUEOUS ACIDIC SOLUTION IN WHICH THEREIS DISSOLVED FROM ABOUT 1/4 TO ABOUT 80 GRAMS PER LITER OF AWATER-SOLUBLE SULFOOXYGEN COMPOUND OF THE GROUP CONSISTING OFUNSATURATED ALIPHATIC SULFONIC ACIDS, MONNUCLEAR AND BINUCLEAR AROMATICSULFONIC ACIDS, HETEROCYCLIC SULFONIC ACIDS, MONONUCLEAR AROMATICSULFINIC ACIDS, THE ALKALI METAL, AMMONIUM, MAGNESIUM, AND NICKEL SALTSOF SAID ACIDS, AND MONONUCLEAR AROMATIC SULFONAMIDES AND SULFONIMIDES,AND FROM ABOUT 1 TO ABOUT 25 MILLIMOLES PER LITER OF A WATER-SOLUBLENISULFITE ADDITON PRODUCT OF AN A-SUBSTITUTED ACETYLENIC COMPOUND AND NTIMES AN EQUIVALENT WEIGHT OF A COMPOUND CAPABLE OF FORMING ACHAIN-CARRYING SULFITE RADICAL, WHERE N IS EQUAL TO THE NUMBER OFACETYLENIC BONDS PER MOLECULE OF THE ACETYLENIC COMPOUND, SAIDA-SUBSTITUTED ACETYLENIC COMPOUND CONTAINING THE STRUCTURALCONFIGURATION